1. Field of the Invention
The present invention is in the field of construction and more specifically relates to a technique for controlling the amount of underground moisture supplied to a surface layer, while simultaneously stabilizing the surface layer. The technique of the present invention is particularly suitable for the construction of clay tennis courts, although it could equally well be applied to agricultural use.
2. The Prior Art
In building railbeds for railroad tracks, it is known to place a layer of ballast stone on the ground as a first layer. The ballast stones are more or less of the same size. The ballast layer permits surface water to flow under the railroad tracks so that the railbed does not act to dam the flow of surface water.
In other structures, a layer of finer rock is sometimes placed on top of the ballast layer, and no effort is made to keep the layers separated. With the passage of time, and under the action of the elements, it is not unusual for the finer upper layer to work its way into the coarser lower ballast layer, thereby filling in the interstices of the ballast layer and thereby reducing its ability to pass the surface water.
In a different field of prior art, it is known to bury perforated pipes in the earth to provide irrigation for the soil. The water supplied to the pipes escapes through the perforations and is released into the soil. This drip irrigation technique, as currently practiced, is an excellent way to supply moisture to a pair of adjacent parallel rows of crops, but the current technique would prove to be hopelessly uneconomical and impractical for creating and maintaining an artificial water table.
In the event of a heavy rain, such an underground watering system can cause flooding because it includes no way of removing water from the ground.
Finally, the use of a system of buried pipes has the disadvantage that if a pipe should break it is very difficult to locate the break, and repair can be effected only by digging up the surface area.
Thus, it is seen that previously known underground watering systems have a number of defects that limit their usefulness.